Metallurgically heat treated metal tubing is used in a wide variety of technical applications. For example annealed (also referred to as soft or ductile) copper tubing is widely used for refrigerant lines in air conditioners and heat pumps. Work hardening in the initial formation of copper tubing makes the copper hard or rigid and it must be annealed to make it soft again for use by an end user.
Long continuous lengths of metallurgically heat treated metal tubing can be produced in different multi-layered configurations at the location of final heat treatment as the end user product for delivery to the end user. For example there is known in the art “level wound coil” (LWC) configurations where typically the metal tubing is wound around a mandrel (bobbin, spool, reel or other shaping tool) on the horizontal where all of the corresponding windings of tubing in each layer are horizontally wound on top of each other (like a cotton reel); hence the terminology “level wound (continuous) coil”.
Additionally end user continuous metal tubing in multi-layer configurations (referred to as “lay stack” herein for convenience) can be differentiated on whether the end user lay stack is formed prior or subsequent to final heat treatment. The two different methods are described herein as an example for copper tubing where the heat treatment is an annealing process but can be used for other types of metal tubing and heat treatment processes.
In the first method of producing an end user lay stack of annealed copper tubing, which can be referred to as a batch tubing heat treatment method, a lay stack of hard copper tubing is first produced and the lay stack of hard copper tubing is placed in a furnace, such as a fossil fuel furnace, or electric element to heat anneal the hard copper tubing to an appropriate (light or soft) annealing temperature. The batch annealed lay stack of copper tubing is then packaged for delivery to an end user of the batch annealed copper tubing where selected lengths of tubing are drawn and cut from the lay stack of annealed copper tubing. In this annealing process the method of winding the layers (also referred to as levels) of the lay stack of hard copper metal tubing is preferably accomplished to satisfy two purposes: minimizing any sticking together of adjacent windings of the tubing in the same layer of the tubing or in adjacent layers above or below a particular layer; and facilitating drawing lengths of the annealed copper tubing from the lay stack of annealed copper metal tubing by the end user.
International patent application PCT/JP2016/054163 discloses a lay stack configuration (also referred to herein as “geometry”) that is identified as a spiral coil lamination (that is, composed of layers) where the metal tubing is spirally wound into an end user product without a mandrel or other shaping tool that can be particularly suited for a batch tubing heat treatment method. With reference to the drawing reference number used in the figures of the application, multiple spiral layers (or levels) (3) formed from the metal tubing (2) are wound into a spiral and layered in the direction in which the central axis of the coil layered body extends. A-layer spiral coils (3a) the innermost side (5a) of which is connected to the innermost side (5b) of a spiral coil one layer higher and the outermost side (4a) of which is connected to the outermost side (4b) of a spiral coil one layer lower; and B-layer spiral coils (3b) the outermost side (4b) of which is connected to the outermost side (4a) of a spiral coil one layer higher and the innermost side (5b) of which is connected to the innermost side (5a) of the spiral coil one layer lower. The A-layer spiral coils (3a) and the B-layer spiral coils (3b) are repeated alternately, and the radius of curvature for the metal tubing (2) of each spiral coil (3) changes continuously and the metal tubing is wound so that the gap between adjacent metal tubing (2) is smaller than the diameter of the metal tubing.
After formation of the spiral coil lamination as described in the previous paragraph, the spiral coil lamination is bundled with a metal band so that the described multi-level spiral configuration (geometry) does not collapse and is then batch annealed in a final annealing furnace to manufacture the end user spiral coil lamination as disclosed in paragraph [0045] of international patent application PCT/JP2016/054163.
A second method of producing a lay stack of annealed copper (or other metal) tubing is to process a continuous length of hard copper tubing equal to the length of continuous tubing in the desired end user lay stack of annealed copper tubing through an annealing heating device, such as an electric inductor (also referred to as an induction coil) annealing system to heat anneal the tubing and then coil the linear length of annealed tubing into a lay stack with a coil stack casting arm as known in the art that feeds the annealed copper tubing into a receiving mechanism as known in the art with a particular multi-layer spiral configuration (or geometry). In this annealing process the method of winding the layers (or levels) of the lay stack of annealed metal tubing is preferably accomplished to facilitate drawing of the annealed metal tubing from the lay stack by the end user.
Most generally the final end user lay stack product of annealed copper tubing consists of adjacent horizontally wound layers of annealed tubing laid down in alternating “outer-radius to inner-radius” winding layers and “inner-radius-to-outer-radius” winding layers.
The end user (final product) lay stack of annealed copper tubing produced by either method can be optionally packaged with support structures to retain the original spirally wound configuration or geometry. However in many instances the packaging of the final product comprises placing the multi-layer spiral configuration of continuous annealed copper tubing (hard copper tubing in the first method above and annealed copper tubing in the second method) on a suitable flat transport structure, such as a pallet, without additional support structures and then shrinking wrapping (or otherwise containing) the lay stack of annealed copper tubing to the flat transport structure for shipping to the end user.